Transfer Factor: Transfer factor is a dialysable moiety of less than 10,000 M.W. which transmits the cellular immunological memories of the donor. The identification and characterization of transfer factor for delayed sensitivity in human leukocytes continues. With this information at hand, an in vitro assay system has been developed and in vivo experiments designed to elucidate the precise mechanism by which this type of immunological information is transmitted from cell-to-cell and how this transaction affects the behavior of cell populations. Complementary to this objective is the initiative of studies designed to explore the role of transfer factor (1) as a general biological activity of cells and its relationship to cell-regulatory mechanisms in diseases and where its manufacture is suspended and (2) as immunotherapy of cancer studying malignant melanoma as a model in conjunction with the Melanoma Study Group of N.Y.U. and (3) as immunotherapy of infectious diseases caused by intracellular bacteria, fungi and viruses. We also propose to continue in vitro experiments designed to isolate and characterize other mediators of cellular immunity such as Lymphocyte Transforming Factor and Lymphotoxin. Transfer Factor specifically recruits normal lymphocytes to an antigen response state and we plan to evaluate whether Lymphocyte Transforming Factor is a specific or nonspecific recruiting agent of normal lymphocytes.